NCI-Agency/anet#707: Only update the marker layer if the array of marker id's has changed
NCI-Agency/anet#707: Only update the marker layer if the array of marker id's has changed

Also HTML-escape the marker pop-up!

NCI-Agency/anet,NCI-Agency/anet,NCI-Agency/anet,NCI-Agency/anet,NCI-Agency/anet